Field of the Invention
This invention relates to electrical duplicating control apparatus, in general and more particularly to an improved control apparatus for duplicating milling machines.
Such apparatus comprising a sensor which scans a model mechanically and has a sensing stylus and coil systems operating orthogonally to each other as the sensing systems, with the output voltages of the sensing systems used to derive velocity control signals for the feed drives in the individual machines axes, and also includes a device which feeds appropriate correction signals to the feed drives for maintaining a predetermined amount of deflection of the sensing stylus is described in German Auslegeschrift No. 1,552,554. In the disclosed device, the velocity (rate) control signals are proportional to the output voltages of the sensing systems. Therefore, there is no possibility of changing the amounts of predetermined sensing stylus deflection and resultant feed velocity independently of each other. Any change of the predetermined amount of sensing stylus deflection also changes the resultant feed velocity. Independently changing the sensing stylus deflection and the feed velocity is important particularly if repeated machining of the same work piece at different distances from the final contour is desired without having to exchange the sensing stylus for another one with a different offset dimension.
Since in the known duplicating control apparatus, only two dimensional deflection of the sensing stylus is provided, the transversal deflection is not picked up if model surfaces not perpendicular to the deflection plane are scanned, and therefore, the dimensional correctness of the work piece is not assured.